1. Field of the Invention
More particularly, the invention relates to a method of processing milk and dairy products, and especially to such a method whereby a liquid enriched cheese milk or liquid retentate product suitable for conversion into cheese may be obtained.
The invention has for its object a process which makes it possible to obtain, starting from milk, a liquid filtration product (filtrate) containing the major part of the liquid content and a major part of the co-called soluble constituents of the initial milk, such as lactose, mineral salts, non-protein nitrogen substances; the percentages at which those various substances are present in this liquid filtrate being, in principle, equal or close to the respective percentages at which they are present in the aqueous phase of milk; and on the other hand, a liquid retentate containing all, or substantially all, the proteins of the initial milk and a minor part of the so-called soluble constituents; the protein content and the soluble constituents content of this liquid being substantially equal to those existing in a cheese prepared from milk at the end of the whey drainage process. Thus, a notable object of the invention is a process making it possible to prepare from milk, such as secreted by the milch-animal, a liquid raw material having substantially the composition of a drained cheese except for its enrichment in soluble proteins, in which the ingredients are present in proportions appropriate for cheese-making.
Thus, it is one object of the invention to provide a process which makes it possible to prepare from milk a retained ultrafiltration liquid raw material, or liquid retentate, suitable for conversion into drained cheese.
2. Description of the Prior Art
In previously known cheese-making processes, the curd is obtained by coagulation of milk as derived from the milch animal, or after fat separation, with rennet. Then, the curd is separated from the whey by drainage, with or without pressing in moulds as it is usually done when making soft cheese, fresh or ripened. On the other hand, when making hard pressed cheese or cooked cheese, the curd is cut and mechanically stirred and heated at varying intensities and then the curd is subjected to decantation and a drawing off of the whey.
In standard cheese making practice, the technological operations carried out from the stage where the milk is coagulated in vats up to the stage where the cheese is drained and moulded are costly in terms of labor and equipment, and the cheese obtained is heterogeneous or variable from the three standpoints of quality, composition and weight of each cheese. Indeed, in the present stage of the art, it is very difficult, if not impossible, to control and to adjust with sufficient accuracy, prior to clot formation with rennet, all the parameters which determine the characteristics of the final cheese.
If the variation in weight from one individual cheese to another has relatively little importance for pressed or cooked types of cheese, which are sold on the basis of their weight, the same does not apply at all for soft cheese, which is sold on an individual cheese basis. In all countries producing soft cheese, the loss or profit, due to the extent or the safety margins adopted by the cheese maker to make up for this variation in weight, represents quite an appreciable percentage of the total turnover. The variation in composition is partly the result of the difficulties experienced during the cheese making operations in heating, cutting or stirring a gel; i.e. the clot formed by the rennet, in which the thermal or mechanical exchanges are much more difficult than inside a liquid. While mixing a liquid as obtained, for instance, by this invention, is easy and insures equal distribution of heat, etc., the same does not hold true for a gel. As regards variation in quality, this is to a large extent the result of the two foregoing factors.
Prior art processes are known for performing in continuous manner the production of curd and thus rationalizing manufacture. In one of these processes, the normal milk, renneted cold, is heated in a heat exchanger; it coagulates and circulates in this form in a coagulation cylinder. In another known process, the milk concentrated by evaporation is heated by mixing it with warm water. Coagulation then takes place instantaneously. Other processes mechanize syneresis (whey drainage) of the clot obtained by the action of the rennet.
However, all these previously known processes have drawbacks and the resulting products are as variable as those obtained by the standard cheese making technique for, as in the latter case, the whey drainage takes place subsequently to coagulation. In addition, the field of application of these various processes is rather narrow and they may be difficult to use because the raw material (i.e. milk) may vary to quite a marked extent (the composition of milk varies according to season, area, etc.). This, in turn, may prevent certain technological requirements associated with these processes from being satisfied. Moreover, these processes require for their implementation installation which are fairly cumbersome.